Today is the 29th anniversary of the Three-Mile Island Nuclear Power Plant Accident.

At *exactly* 4am on March 28th 1979, the cooling system's main feedwater pumps for the non-nuclear water circuit on Reactor 2 failed. Between 11am and 1:30pm, 13 million curies of noble gases were released into the environment, including 20 curies of Iodine-131.

The average radiation dose to people living within ten miles of the plant was eight millirem, and no more than 100 millirem to any single individual. Eight millirem is about equal to a chest X-ray, and 100 millirem is about a third of the average background level of radiation received by US residents in a year.

http://en.wikipedia.org/wiki/Three_Mile_Island_accident